[nebnacnud]

Hi, I'm looking at buying an ultrabudget set of bookshelf speakers for my room, but I don't know much about power ratings and amps. The speakers I'm looking at have a power capacity of 80 watts, an impedance of 8 ohms, and a sensitivity of 89db. The amp I am considering is rated for an output of 20 watts per speaker.
 
I read somewhere that the 80 watts for the speaker is the maximum it can handle before it is damaged, but the amp is only rated for 20 watts (which I read is the power output at 100% volume). Will the amp be able to drive the speakers? What causes distortion in a system? Will an under-rated amp distort when raising the volume? And how loud should the speakers be able to get with this setup?
 
I am also open to considering other speakers or amps in the price range if there are better options, but I don't have the money to go much higher than this. Also, If I am posting this in the wrong forum, please direct me to the correct location. I tried posting in the "Introductions, Help and Recommendations" forum first because I wasn't sure if this should go here, but I haven't gotten any replies so I figured I might as well go ahead.

Thanks in advance for any help!

 

[PleasantSounds]

I don't know much about these speakers, but both Monoprice and Lepai seem to enjoy pretty good reputation around here, at least in terms of value for money. I doubt you will find something substantially better in this price range.
 
Regarding the 80W/20W pairing: it all depends on how you intend to use these speakers. For desktop use in a smallish room this will be more than enough. At my desk I used for several years 150W speakers with 2x15W amp and the sound was very good, while the volume pot hardly ever crossed 12 o'clock.

 

[nebnacnud]

They should definitely be fine for my purposes in a small dorm room then. Thanks for clearing up my questions!

 

[cel4145]

If an amp is pushed past its limits, it can clip, causing distortion which can damage speakers.

If an amp is more powerful than speakers, and you push the speakers past their limit where they distort, they can be damaged.

So no matter which way you go (less powerful/more powerful amp than the speakers), the best practice is don't run your amp so loud that the speakers start to distort.

 

[nebnacnud]

So regarding the first scenario, would that be accomplished by providing the amp with too strong a signal from the line in?

 

[cel4145]

So regarding the first scenario, would that be accomplished by providing the amp with too strong a signal from the line in?

I don't know what you mean.

 

[nebnacnud]

Sorry. Would you overdrive the amp by raising the volume of the source, or the volume of the amp itself?

 

[cel4145]

If you crank any amp all the way up, you could potentially drive the amp to clipping.

The trick is, don't worry about any of that. You have to learn where the limits are of your speaker/amp where you start to hear distortion, and then don't turn it up that high. There is no substitute for learning that. People that don't learn that are the ones that blow speakers.

 

[PleasantSounds]

If an amp is pushed past its limits, it can clip, causing distortion which can damage speakers.

If an amp is more powerful than speakers, and you push the speakers past their limit where they distort, they can be damaged.

So no matter which way you go (less powerful/more powerful amp than the speakers), the best practice is don't run your amp so loud that the speakers start to distort.

 
Can you please expand a bit on how distortion could damage speakers, if the overall power output is still within the capabilities of speakers? That's a new theory to me.

 

[cel4145]

Can you please expand a bit on how distortion could damage speakers, if the overall power output is still within the capabilities of speakers? That's a new theory to me.

No. Because I'm not an engineer. LOL

But not a new theory, rather science. This guy is a speaker designer who regularly explains it over at AVS: http://www.avsforum.com/forum/155-diy-speakers-subs/1455776-damaging-clip-amp.html#post22919040

 

[PleasantSounds]

No. Because I'm not an engineer. LOL

But not a new theory, rather science. This guy is a speaker designer who regularly explains it over at AVS: http://www.avsforum.com/forum/155-diy-speakers-subs/1455776-damaging-clip-amp.html#post22919040

 
I've read that post and while I agree with the author, it is not really relevant in this case. Following his line of arguing, if a 20W amp outputs even 50% of power in the high frequency range, that is only 12.5% of the 80W speaker's nominal power - something that a tweeter should be able to handle. In practice the sound will be so awful that you'll turn the volume down long before it becomes dangerous for the speakers.
 
In fact an amp which is matched power wise to the speakers is more likely to damage them when you overload it.

 

[cel4145]

I've read that post and while I agree with the author, it is not really relevant in this case. Following his line of arguing, if a 20W amp outputs even 50% of power in the high frequency range, that is only 12.5% of the 80W speaker's nominal power - something that a tweeter should be able to handle. In practice the sound will be so awful that you'll turn the volume down long before it becomes dangerous for the speakers.

I strongly disagree because (a) manufacturer's play pretty loose with their speaker ratings, (b) you have no idea of the amp's maximum output, and (c) there's absolutely no good reason to run the risk based upon a guess. Too many variables to take a risk. Although I guess it's easy enough to do with someone else's money/equipment.

 

[PleasantSounds]

I strongly disagree because (a) manufacturer's play pretty loose with their speaker ratings, (b) you have no idea of the amp's maximum output, and (c) there's absolutely no good reason to run the risk based upon a guess. Too many variables to take a risk. Although I guess it's easy enough to do with someone else's money/equipment.

 
Clutching at straws are we?
 
(a) so we are safe when the loose specs match, but when there's a margin it's suddenly high risk?
(b) at 12V power supply that the Lepai takes and 8 Ohm impedance of the speakers, the maximum they will be hit wioth is 18W. In fact it will be less because the power supply outputs only 2A, so you have 24W to split between both channels.
(c) where is the risk? do you even undestand anything about electronics? You have conveniently omitted the key point:
 
In fact an amp which is matched power wise to the speakers is more likely to damage them when you overload it.
 
Using an amp with lower power rating than the speakers reduces the risk of blowing them up, not increases.

 

[Solrighal]

I've always been led to believe that overdriving a weak amp is more dangerous than using a powerful amp. Surely the listeners ears play a part here. If it sounds too loud then it is too loud. Turn it down.

 

[cel4145]

Clutching at straws are we?

(a) so we are safe when the loose specs match, but when there's a margin it's suddenly high risk?

No. Who said anything about being safe when the loose specs match? We know that manufacturer specs are all over the place when it comes to accuracy regarding amps and speakers.

(b) at 12V power supply that the Lepai takes and 8 Ohm impedance of the speakers, the maximum they will be hit wioth is 18W. In fact it will be less because the power supply outputs only 2A, so you have 24W to split between both channels.

My bad. I didn't realize he was specifying the Lepai and the Monoprice speakers. However, how do you know what load the speakers present to the amp? Speakers typically vary quite a bit in impedance across the frequency range, and the impedance rating is often not accurate. For example, http://www.audioholics.com/tower-speaker-reviews/pioneer-sp-pk52fs/pioneer-sp-pk52fs-measurements. If you need more examples, go look at a lot of speaker measurements and you'll soon learn how untrustworthy they are.

(c) where is the risk? do you even undestand anything about electronics? You have conveniently omitted the key point:

In fact an amp which is matched power wise to the speakers is more likely to damage them when you overload it.

Using an amp with lower power rating than the speakers reduces the risk of blowing them up, not increases.

That doesn't mean there is no risk. And are you an engineer? I don't have to be one to know that you have not provided enough information here to accurately predict whether or not it's risky to crank that amp all the way up with those speakers.